This invention relates generally to portable supports and more particularly to such supports suitable for holding surveying equipment and the like.
Although the art of surveying is old, recent improvements in equipment, such as automatic electronic total surveying stations, have increased the accuracy of the surveying instruments far beyond what was possible previously. Where accepted accuracy for equipment in the not too distance past was 20 seconds of a degree, accuracy is now commonly required to be 1 second of a degree. At these levels of precision, the instruments must be supported in a manner which is consistent and stable. Accordingly, there is a need for closer examination of support structure used for surveying equipment so that improvements in instrumentation will not be lessened by inadequate supports.
A most common support for surveying equipment is the tripod with telescoping legs that can be retracted for carrying and storage. Certainly bipods are also employed in surveying, and conceivably any number of legs could be provided, but the three point support remains the most common. Frequently, surveying is done far from roads or sidewalks so equipment may have to be carried over broken terrain for considerable distances to reach the site. As a result, it is imperative that the tripod be able to collapse for easy transportation. However, the ability to collapse can be the source of imprecision in supporting the equipment when the site is reached. Movement thereafter, even on a scale which would not be readily perceptible to the surveyors, can detrimentally affect the accuracy of the supported equipment. Presently, the hinged connection of the legs to the head is exposed to ingress of debris which can damage the hinge causing play in the hinge and a loss of rigid stability of the support needed to accurately position the surveying equipment. Traditional hinge connections do little to prevent debris from entering. Moreover, the connection is such that only a limited amount of lubricant can be used in the connection. Although it is possible to use other materials to reduce friction in the hinge, it is better to maintain metal-to-metal contact in the hinge for superior performance.
Loss of alignment and play may also occur in the connection of the center leg member to a foot which engages the ground. Some tripods have removable feet which permit attachment of different ground engaging accessories suitable for different surfaces and conditions. The releasable connection may give rise to looseness and some small motion or loss of alignment between the center leg member and the foot detrimental to accuracy. However, even a conventional permanent connection may lack the rigidity and strength desirable.
Features of convenience are usually neglected in a conventional tripod. At most, a strap is attached to one of the legs which can be wrapped around the legs and secured to hold the legs together in their collapsed configuration. However, little has been done to provide an easy, nearly automatic way of securing the legs in the collapsed position. Moreover, carrying the tripod is not facilitated. Most commonly the tripod is hoisted onto one or both shoulders for carrying, which also has the advantage of holding the legs together in the collapsed position without having to tie them. Thus, transporting the tripod can easily occupy both hands. The other surveying tools and equipment which will be needed are carried separately. It is not practical to mount anything on the most accessible, broad surface of the tripod, which is the front face of the center leg member. The front face must in telescoping with respect to the rods pass under a retainer at the end of the rods necessary to hold the rods in a fixed lateral spacing. Therefore, surveying tools and equipment are usually carried separately in a bag or other container.
Among the accessories needed is additional weight for one or more of the tripod legs. In some circumstances, such as when there are high winds, the tripod can move. To combat this, weight is added to the legs often by draping weighted bags over the legs. The bags are not attached to the legs and so can shift or fall off.
Among the several objects and features of the present invention may be noted the provision of a support for surveying equipment which provides a stable and rigid platform for high precision surveying equipment; the provision of such a support which can be made of lighter weight material; the provision of such a support which is made of material which is not subject to plastic deformation; the provision of such a support which has legs constructed to resist lateral loads; the provision of such a support which is easy to transport; the provision of such a support which is self retained in a collapsed position; the provision of such a support which holds accessories and equipment; the provision of such a support which can be readily reconfigured for different ground conditions; the provision of such a support which mounts additional ballast needed; the provision of such a support which can be manufactured with high precision; and the provision of such a support which can be manufactured economically.
Further among the several objects and features of the present invention may be noted the provision of a method of reconfiguring a portable support which can be done quickly and easily; the provision of such a method which does not require any substantial disassembly of the base support structure; the provision of such a method which rigidly mounts accessories on the support; and the provision of such a method which provides two points of attachment for an accessory.
Generally, a leg for a portable support for use in supporting equipment a above a surface comprises a fixed leg member and a telescoping leg member connected to the fixed leg member for sliding motion relative to the leg member between a fully extended position and a fully retracted position. A clamp has a locked position for selectively securing the telescoping leg member in a selected position relative to the fixed leg member, and an unlocked position in which the telescoping leg member is movable relative to the fixed leg member. A foot at a bottom end of each telescoping leg for engaging the surface is adapted to mount at least one surface engaging accessory thereon.
In a further aspect of the present invention, a leg for a portable support for use in supporting equipment above a surface generally comprises a fixed leg member, a telescoping leg member and a clamp as set forth above. A foot at a bottom end of each telescoping leg for engaging the surface is connected to the telescoping leg member by an adhesive.
In a still further aspect of the present invention a leg for a portable support for use in supporting equipment above a surface generally comprises a fixed leg member, a telescoping leg member and a clamp as set forth. A foot at a bottom end of each telescoping leg for engaging the surface has a ring formed as one piece with the foot and projecting laterally outwardly therefrom.
In another aspect of the present invention, a method of converting the structure on legs of a portable support which engages a surface above which the portable support holds equipment generally comprising the step of providing feet permanently attached to the legs and constituting part of the legs. The leg is adapted for engaging the surface in a first configuration of the portable support. Alternative ground engaging accessories are attached to the legs at least at two spaced apart locations on each leg such that each alternative ground engaging accessory extends below the foot for engaging the surface.
In yet another aspect of the present invention, a method of forming a leg for a portable support used to support equipment above a surface generally comprises the step of providing a fixed leg member and a telescoping leg member adapted to be slidingly mounted on the fixed leg member for movement between a fully extending position and a fully retracted position. A lower end of the telescoping leg is inserted into the foot such that the telescoping leg engages the foot on the interior thereof locating the foot relative to the leg in a predetermined position. The foot is adhered to the lower end of the telescoping leg.
In a further aspect of the present invention, a portable support for supporting equipment above a surface generally comprises a head for holding the equipment, and legs connected to the head for supporting the head above the surface. The legs include a hinge pin projecting outward from the leg generally at an upper end thereof and the head includes a hinge pin receptacle receiving the hinge pin in sealed relation with the hinge pin to inhibit debris from affecting the operation of the hinge pin to pivot the leg.
In a still further aspect of the present invention, a portable support for supporting equipment above a surface generally comprises a head for holding the equipment, and legs connected to the head for supporting the head above the surface and for pivoting between a use position in which the legs are spread apart and a collapsed position in which the legs are closer together than in the use position for transportation and storage. The legs having connector elements which are positioned to interengage each other when the legs are moved to the collapsed position for holding the legs in the collapsed position.
In another aspect of the present invention, a weight for selectively mounting on a leg of a portable support for use in supporting equipment above a surface generally comprises a container and flexible connectors attached to the container and adapted to extend around the leg. The flexible connectors are capable of holding the weight in self-retaining position on the leg.
In still another aspect of the present invention, a portable support for use in supporting equipment above a surface comprises a head for holding the equipment, legs connected to the head for supporting the head above the surface and feet on the bottom end of each leg. The legs include a point for penetrating the surface in normal use of the portable support and spikes adapted for connection to each of the legs in a position such that the spikes project substantially below the point for securing the support in position.
In yet another aspect of the present invention, a portable support for use in supporting equipment above a surface generally comprises a head for holding the equipment, legs connected to the head for supporting the head above the surface and feet on the bottom end of each leg. A weight is adapted for fixedly mounting on the leg.
Other objects and features of the present invention will be in part apparent and in part pointed out hereinafter.